detectLanguage.js

detectBrowserlanguage(defaultLang) {
    const navLang = navigator.language || navigator.userLanguage || defaultLang;
    return navLang.substring(0, 2);
}

componentDidMount() {
    const defaultLang = this.detectBrowserlanguage("en");
    const lang = localStorage.getItem("user-lang");
    const usedLang = lang ? lang : defaultLang;

    this.setState(
    {
      lang: usedLang
    },
    //() => {
    //  i18n.changeLanguage(this.state.lang, () => {
    //    this.lnNotifier.emit("langChanged");
    //  });
    //}
    );
}